Champagne is a sparkling
wine produced by inducing the in-bottle secondary fermentation of wine
to effect carbonation. It is produced exclusively within the Champagne
region of France, from which it takes its name. While the term "champagne" is
used by some makers of sparkling wine in other parts of the world, numerous
countries limit the use of the term to only those wines that come from
the Champagne appellation. In Europe, this principle is enshrined in
the European Union by Protected Designation of Origin (PDO) status. Other
countries, such as the United States, have recognized the exclusive nature
of this name, yet maintain a legal structure that allows longtime domestic
producers of sparkling wine to continue to use the term "Champagne" under
specific circumstances.
There are different types of Champagne. Brut is the driest, and the "standard". If you want to get a "great" Champagne, go for a Brut. Extra-dry is less dry than Brut. Sec is sweet, and Demi Sec is even sweeter.

The Champagne market is extremely cyclical. Normally 50% of all Champagne is sold from January through the end of November. Then, 25% is sold up until Christmas Day. A full quarter of all Champagne sold is sold during that final week between Christmas and New Years!